Cash and cash equivalents and short-term investments.

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Cash And Cash Equivalents At Carrying Value And Available For Sale Securities Debt Securities Current.

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Cash And Cash Equivalents At Carrying Value Available And Available For Sale Debt Securities Amortized Cost Basis.

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Cash equivalents at carrying value and available for sale debt securities amortized cost basis.

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Cash equivalents at carrying value and available for sale securities debt securities current.

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Cash, Cash Equivalents and Short-Term Investments - Schedule of Cash and Cash Equivalents and Short-term Investments by Significant Investment Category (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Cash And Cash Equivalents And Short Term Investments [Line Items]
Cash	$ 2,564	$ 3,044
Short term investments Gross Unrealized Gains	13
Short term investments Gross Unrealized Losses		(9)
Short term investments	20,572	20,169
Cash and cash equivalents and Short term investments, Amortized Cost	34,200	33,799
Cash and cash equivalents and Short term investments, Estimated Fair Value	34,213	33,790
Cash and cash equivalents	13,641	13,621	$ 13,259	$ 15,026
Level 1
Cash And Cash Equivalents And Short Term Investments [Line Items]
Short term investments Gross Unrealized Gains	6
Cash equivalents and Short term investments, Estimated Fair Value	11,524	7,470
Cash equivalents and Short term investments, Amortized Cost	11,518	7,470
Level 2
Cash And Cash Equivalents And Short Term Investments [Line Items]
Short term investments Gross Unrealized Gains	7
Short term investments Gross Unrealized Losses		(9)
Short term investments	15,576	18,181
Cash equivalents and Short term investments, Estimated Fair Value	20,125	23,276
Cash and cash equivalents	4,549	5,095
Cash equivalents and Short term investments, Amortized Cost	20,118	23,285
Money Market Funds \| Level 1
Cash And Cash Equivalents And Short Term Investments [Line Items]
Cash equivalents	6,528	5,482
Repurchase Agreements \| Level 2
Cash And Cash Equivalents And Short Term Investments [Line Items]
Cash equivalents	3,001	3,000
US Treasury Securities \| Level 1
Cash And Cash Equivalents And Short Term Investments [Line Items]
Short Term Investments Amortized Cost	4,990	1,988
Short term investments Gross Unrealized Gains	6
Short term investments	4,996	1,988
Commercial Paper \| Level 2
Cash And Cash Equivalents And Short Term Investments [Line Items]
Cash equivalents	1,548	2,095
Short Term Investments Amortized Cost	9,678	10,639
Short term investments	8,130	8,544
Cash equivalents and Short term investments, Estimated Fair Value	9,678	10,639
Corporate Debt Securities \| Level 2
Cash And Cash Equivalents And Short Term Investments [Line Items]
Short Term Investments Amortized Cost	3,038	5,964
Short term investments Gross Unrealized Gains	4
Short term investments Gross Unrealized Losses		(7)
Short term investments	3,042	5,957
Asset-backed Securities \| Level 2
Cash And Cash Equivalents And Short Term Investments [Line Items]
Short Term Investments Amortized Cost	4,401	3,682
Short term investments Gross Unrealized Gains	3
Short term investments Gross Unrealized Losses		(2)
Short term investments	4,404	3,680
Cash equivalents and Short term investments, Estimated Fair Value	$ 4,404	$ 3,680